U.S. Pat. No. 4,754,247 describes an industrial-rated circuit breaker utilizing an electronic trip unit to articulate the circuit breaker operating mechanism upon the occurrence of an overcurrent condition through a protected circuit. The circuit breaker includes an accessory cover that allows field as well as factory installation of selected circuit breaker accessories by providing access to the accessory recesses formed within the circuit breaker cover without affecting the integrity of the circuit breaker operating components contained within the circuit breaker case.
An actuator-accessory unit such as described in U.S. Pat. No. 4,788,621 provides undervoltage release as well as shunt trip function to such circuit breakers when mounted within the accessory recess. U.S. Pat. No. 4,939,490 describes a bell alarm unit accessory that is often used in combination with the aforementioned undervoltage release and shunt trip accessory unit.
U.S. patent application Ser. No. 650,275 entitled "Molded Case Circuit Breaker Thermal-Magnetic Trip Accelerator" describes an industrial-rated circuit breaker employing a thermal-magnetic trip unit for articulating the circuit breaker operating mechanism upon the occurrence of overcurrent conditions within a protected circuit. The aforementioned U.S. Pat. No. 4,754,247 employing an electronic trip unit simplifies the use of such accessories by virtue of electronic communication with the actuator-accessory unit that is contained within the accessory recess. The thermal-magnetic trip unit used within the aforementioned U.S. patent application Ser. No. 650,275 does not provide an electronic output and hence the accessories must be capable of directly articulating the circuit breaker operating mechanism, per se.
Accordingly, one purpose of the invention is to describe circuit breaker accessory units that are both field and factory installable within such industrial-rated circuit breakers employing thermal-magnetic trip units.